The present invention relates in general to surgical stapler instruments which are capable of applying lines of staples to tissue while cutting the tissue between those staple lines and, more particularly, to improvements relating to stapler instruments and improvements in processes for forming various components of such stapler instruments.
Surgical staplers have been used in the prior art to simultaneously make a longitudinal incision in tissue and apply lines of staples on opposing sides of the incision. Such instruments commonly include a pair of cooperating jaw members which, if the instrument is intended for endoscopic or laparoscopic applications, are capable of passing through a cannula passageway. One of the jaw members receives a staple cartridge having at least two laterally spaced rows of staples. The other jaw member defines an anvil having staple-forming pockets aligned with the rows of staples in the cartridge. The instrument includes a plurality of reciprocating wedges which, when driven distally, pass through openings in the staple cartridge and engage drivers supporting the staples to effect the firing of the staples toward the anvil.
In the art there are described means for gauging tissue thickness between the jaws of a linear cutter stapler. Use of these means are cumbersome, in that they require a separate mechanism to be provided at the site in order to measure tissue thickness. Thus, there is a need for a device which is located in the stapler, and is capable of determining tissue gathered between the jaws of the instrument.
The wedges are commonly formed from metal and assembled in a pusher block to form a single component. Since a number of individual parts must be assembled to form this component, it is costly to manufacture. Also, such components, because they are comprised of a number of individual parts, oftentimes have less than optimum stability. Further, it has been found that use of metal wedges results in a high coefficient of friction between the wedges and the drivers during staple firing.
The prior art wedges generally include a straight, single-angle cam surface. The cam surface is designed to provide sufficient force for bending over ends of the staples. While the cam design performs the desired operation, it also results in an undesirable increase in the overall length of the instrument.
Prior art mechanisms for driving wedges distally into a staple cartridge commonly include a firing mechanism and a motion transfer mechanism. The firing mechanism is engaged by a surgeon to effect staple firing. Most currently available motion transfer mechanisms, which are interposed between the firing mechanism and the pusher block, are not easily modifiable for use in stapler instruments having different staple line lengths and/or staple firing force requirements so as to permit, for a given instrument, the length of the stroke of the firing mechanism and the force required to move it to be set at ergonomically preferred values.
Surgical staplers which fire a plurality of rows of staples from an elongated cartridge against an anvil typically have clamping and firing triggers. When the clamping trigger is actuated, tissue placed between the cartridge and anvil is clamped as the anvil moves toward the cartridge into a closed position. When the anvil is moved to the closed position, the user can actuate the firing trigger to drive the staples from the cartridge, through the tissue, and against the anvil for staple formation. Unfortunately, if excessively thick tissue is clamped between the cartridge and anvil when the clamping trigger is actuated, the staples will misform when the firing trigger is actuated. If the staples are misformed when fired into the tissue, then the tissue will not be properly fastened.
After a user actuates the clamping and firing triggers of a surgical stapler, the firing and clamping triggers must return to their unactuated positions so that the user can release the fastened tissue from the stapler. The triggers are typically biased toward their unactuated positions using one or more return springs. In some instances, however, the firing trigger will "stick" in its actuated position after firing because the return spring is unable to overcome the force generated when the staples were driven into the clamped tissue. The user must then manually return the firing trigger from its actuated position to its unactuated position, which is cumbersome and inefficient. Although a larger return spring for the firing trigger could be used to positively overcome the forces generated from firing, to do so would in turn increase the force necessary to fire the staples when the trigger is actuated.
Accordingly, there is a need for an improved stapler instrument. Preferably, such an instrument would have wedges integrally formed as a single unit. Also, the improved stapler instrument would have wedges which are formed from an improved material such that the coefficient of friction between the wedges and the drivers during staple firing is reduced over that found in the prior art. The improved stapler would also have wedges provided with a more efficient cam surface profile. There is further a need for an improved motion transfer mechanism which is easily adaptable for use in various stapler instruments having different staple line lengths and/or staple firing force requirements so as to permit, for a given instrument, the length of the stroke of the firing mechanism and the force required to move it to be set at ergonomically preferred values.
In addition, there is a need for an improved stapler instrument which prevents the user from securing and maintaining excessively thick tissue in a clamped position. There is also a need to provide a mechanism to facilitate the return of the firing trigger from its actuated position to its unactuated position without increasing the size of the return spring for the firing trigger.